246 DIGESTION. 



but careful observations on the comparative action of acidulated water and of artificial 

 or natural gastric juice show that the presence of the organic matter is necessary to 

 the digestion of this as well as of other nitrogenized alimentary principles. The action of 

 water containing a small proportion of acid is to render fibrin soft and transparent, fre- 

 quently giving to the entire mass a jelly-like consistence. The result of the digestion of 

 fibrin in the gastric juice, or in an acidulated fluid to which pepsin has been added, is 

 its complete solution and transformation into a substance which is not affected by heat, 

 acids, or by rennet. 



The substance resulting from the action of gastric juice upon fibrin, called by Leh- 

 mann, fibrin-peptone, presents many points of similarity with the albumen-peptone, but 

 nevertheless has certain distinctive characters. Lehrnann, indeed, supposes that there are 

 differences between the products of the digestion of all the various nitrogenized aliment- 

 ary principles, sufficiently well marked to distinguish them from each other. 



Liquid caseine is immediately coagulated by the gastric juice, by virtue both of the 

 free acid and the organic matter. Once coagulated, caseine is acted upon in the same 

 way as coagulated albumen. The caseine which is taken as an ingredient of cheese is 

 digested in the same way. According to Lehmann, coagulated caseine requires a longer 

 time for its solution in the stomach than most other nitrogenized substances ; and it is 

 stated by the same author, on the authority of Elsasser, that the caseine of human milk, 

 which coagulates only into a sort of jelly, is more easily digested than caseine from cow's 

 milk. The product of the digestion of caseine is a soluble substance, not coagulable by 

 heat or the acids, called by Lehmann, caseine-peptone. 



Gelatine is rapidly dissolved in the gastric juice, when it loses the characters by 

 which it is ordinarily recognized, and no longer forms a jelly on cooling. This substance 

 is much more rapidly disposed of than the tissues from which it is formed, and the prod- 

 ucts of its digestion in the gastric juice resemble the substances resulting from the di- 

 gestion of the albuminoids generally. 



Action on Vegetable Nitrogenized Principles. These principles, of which gluten may 

 be taken as the type, undoubtedly are chiefly, if not entirely digested in the stomach. 

 Raw gluten is acted upon very much in the same way as fibrin, and cooked gluten be- 

 haves like coagulated albumen. Vegetable articles of food generally contain gluten in 

 greater or less quantity, or principles resembling it, as well as various non-nitrogenized 

 principles, and cellulose. The fact that these articles are not easily attacked in any por- 

 tion of the alimentary canal, unless they have been well comminuted in the mouth, is 

 shown by the passage of grains of corn, beans, etc., in the fa3ces. When properly pre- 

 pared by mastication and insalivation, the action of the gastric juice is to disintegrate 

 them, dissolving out the nitrogenized principles, freeing the starch and other matters so 

 that they may be more easily acted upon in the intestines, and leaving the hard, indi- 

 gestible matters, such as cellulose, to pass away in the faeces. The nitrogenized portions 

 of bread are probably acted upon in the stomach in the same way and to the same ex- 

 tent as albumen, fibrin, and caseine. 



Albuminose, or Peptones. 



The product or the sum of the products of the digestion of nitrogenized alimentary 

 principles in the stomach was first closely studied by Mialhe, who regarded the action 

 of the gastric juice on all principles of this class as resulting in their transformation into 

 a new substance which he called albuminose. Lehmann has since investigated the prin- 

 ciples resulting from the action of the gastric juice on various nitrogenized matters and 

 describes them under the name of peptones. It has been conclusively shown that stom- 

 ach-digestion is not merely a solution of certain alimentary principles, but that these 

 substances undergo very marked changes and lose the properties by which they are gen- 

 erally recognized. That the different principles resulting from this transformation re- 



